Tue·Aug 16, 2016Tuesday·August 16, 2016

1. 01*

   Common Origin of Neutrino Mass, Dark Matter and Dirac Leptogenesis

   Debasish Borah🇮🇳 · Arnab Dasgupta🇮🇳

   We study the possibility of generating tiny Dirac neutrino masses at one loop level through the \textit{scotogenic} mechanism such that one of the particles going inside the loop can be a stable cold dark matter (DM) candidate. Majorana mass terms of singlet fermions as well as tree level Dirac neutrino masses are prevented by incorporating the presence of additional discrete symmetries in a minimal fashion, which also guarantee the stability of the dark matter candidate. Due to the absence of total lepton number violation, the observed baryon asymmetry of the Universe is generated through the mechanism of Dirac leptogenesis where an equal and opposite amount of leptonic asymmetry is generated in the left and right handed sectors which are prevented from equilibration due to tiny Dirac Yukawa couplings. Dark matter relic abundance is generated through its usual freeze-out at a temperature much below the scale of leptogenesis. We constrain the relevant parameter space from neutrino mass, baryon asymmetry, Planck bound on dark matter relic abundance, and latest LUX bound on spin independent DM-nucleon scattering cross section. We also discuss the charged lepton flavour violation $(\mu \to e\gamma )$ and electric dipole moment of electron in this model in the light of the latest experimental data and constrain the parameter space of the model.

   hep-phastro-ph.COJCAP(2016)·68 citations
2. 02*

   Dirac dark matter and $b\to s{\ell }^{+}{\ell }^{-}$ with $\mathrm{U}(1)$ gauge symmetry

   Alejandro Celis🇩🇪 · Wan-Zhe Feng🇺🇸 · Martin Vollmann🇩🇪

   We revisit the possibility of a Dirac fermion dark matter candidate in the light of current $b\to s{\ell }^{+}{\ell }^{-}$ anomalies by investigating a minimal extension of the Standard Model with a horizontal ${\mathrm{U}(1)}^{\prime }$ local symmetry. Dark matter stability is protected by a remnant ${\mathcal{Z}}_2$ symmetry arising after spontaneous symmetry breaking of ${\mathrm{U}(1)}^{\prime }$. The associated $Z^{\prime }$ gauge boson can accommodate current hints of new physics in $b\to s{\ell }^{+}{\ell }^{-}$ decays, and acts as a vector portal between dark matter and the visible sector. We find that the model is severely constrained by a combination of precision measurements at flavour factories, LHC searches for dilepton resonances, as well as direct and indirect dark matter searches. Despite this, viable regions of the parameter space accommodating the observed dark matter relic abundance and the $b\to s{\ell }^{+}{\ell }^{-}$ anomalies still persist for dark matter and $Z^{\prime }$ masses in the TeV range.

   hep-phPRD(2017)·48 citations
3. 03*

   Heavy pentaquark states and a novel color structure

   Chengrong Deng🇨🇳 · Jialun Ping🇨🇳 · Hongxia Huang🇨🇳 · Fan Wang🇨🇳

   Encouraged by the observation of the pentaquark states $P_c^{+}(4380)$ and $P_c^{+}(4450)$, we propose a novel color flux-tube structure, pentagonal state, for pentaquark states within the framework of color flux-tube mode involving a five-body confinement potential. Numerical results on the heavy pentaquark states indicate that the states with three color flux-tube structures, diquark, octet and pentagonal structures, have the close masses, which can therefore be called QCD isomers analogous to isomers in Chemistry. The pentagonal structure has lowest energy. The state $P_c^{+}(4380)$ can be described as the compact pentaquark state $uudc\bar{c}$ with the pentagonal structure and $J^P={\frac{3}{2}}^{-}$ in the color flux-tube model. The state $P_c^{+}(4450)$ can not be accommodated into the color flux-tube model. The heavy pentaquark states $uudc\bar{b}$, $uudb\bar{c}$ and $uudb\bar{b}$ are predicted in the color flux-tube model. The five-body confinement potential basing on the color flux-tube picture as a collective degree of freedom is a dynamical mechanism in the formation of the compact heavy pentaquark states.

   hep-phPRD(2017)·28 citations
4. 04*

   Standard Coupling Unification in SO(10), Hybrid Seesaw Neutrino Mass and Leptogenesis, Dark Matter, and Proton Lifetime Predictions

   M. K. Parida🇮🇳 · Bidyut Prava Nayak🇮🇳 · Rajesh Satpathy (Siksha 'O' Anusandhan Univ.)🇮🇳 · Ram Lal Awasthi (IISER, Manauli)🇮🇳

   We discuss gauge coupling unification of the SM descending directly from SO(10) while providing solutions to the three outstanding problems: neutrino masses, dark matter, and the baryon asymmetry of the universe. Conservation of matter parity as gauged discrete symmetry in the model calls for high-scale spontaneous symmetry breaking through ${126}_H$ Higgs representation. This naturally leads to the hybrid seesaw formula for neutrino masses mediated by heavy scalar triplet and right-handed neutrinos. The seesaw formula predicts two distinct patterns of RH$\nu$ masses, one hierarchical and another not so hierarchical (or compact) when fitted with the neutrino oscillation data. Predictions of the baryon asymmetry via leptogenesis are investigated through the decays of both the patterns of RH$\nu$ masses. A complete flavor analysis has been carried out to compute CP-asymmetries and solutions to Boltzmann equations have been utilized to predict the baryon asymmetry. The additional contribution to vertex correction mediated by the heavy left-handed triplet scalar is noted to contribute as dominantly as other Feynman diagrams. We have found successful predictions of the baryon asymmetry for both the patterns of RH$\nu$ masses. The triplet fermionic dark matter at the TeV scale carrying even matter parity is naturally embedded into the non-standard fermionic representation ${45}_F$ of SO(10). In addition to the triplet scalar and the triplet fermion, the model needs a nonstandard color octet fermion of mass $\sim 10^7$ GeV to achieve precision gauge coupling unification. Threshold corrections due to superheavy components of ${126}_H$ and other representations are estimated and found to be substantial. It is noted that the proton life time predicted by the model is accessible to the ongoing and planned experiments over a wide range of parameter space.

   hep-phJHEP(2017)·29 citations
5. 05*

   Search for doubly-heavy dibaryons in a quark model

   J. Vijande🇪🇸 · A. Valcarce🇪🇸 · J.-M. Richard🇫🇷 · P. Sorba🇫🇷

   We study the stability of hexaquark systems containing two heavy quarks and four light quarks within a simple quark model. No bound or metastable state is found. The reason stems on a delicate interplay between chromoelectric and chromomagnetic effects. Our calculation provides also information about anticharmed pentaquarks that are seemingly unbound in simple quark models.

   hep-phnucl-thPRD(2016)·32 citations
6. 06*

   Hadronic molecules with a $\bar{D}$ meson in a medium

   T. F. Caramés🇪🇸 · C. E. Fontoura🇧🇷 · G. Krein🇧🇷 · K. Tsushima🇧🇷 · J. Vijande🇪🇸 · A. Valcarce🇪🇸

   We study the effect of a hot and dense medium on the binding energy of hadronic molecules with open-charm mesons. We focus on a recent chiral quark-model-based prediction of a molecular state in the $N\bar{D}$ system. We analyze how the two-body thresholds and the hadron-hadron interactions are modified when quark and meson masses and quark-meson couplings change in a function of the temperature and baryon density according to predictions of the Nambu--Jona-Lasinio model. We find that in some cases the molecular binding is enhanced in medium as compared to their free-space binding. We discuss the consequences of our findings for the search for exotic hadrons in high-energy heavy-ion collisions as well as in the forthcoming facilities FAIR or J-PARC.

   hep-phnucl-thPRD(2016)·15 citations
7. 07*

   Interpretations of the possible 42.7 GeV $\gamma$-ray line

   Lei Feng🇨🇳 · Yun-Feng Liang🇨🇳 · Tie-Kuang Dong🇨🇳 · Yi-Zhong Fan🇨🇳

   Recently Liang et al. found a tentative line signal at about 43 GeV in the directions of sixteen nearby Galaxy Clusters. If arising from dark matter annihilation, the mass of the dark matter particles should be $m_{\chi }\sim 43$ GeV and the annihilation cross section $⟨\sigma v⟩\sim 5\times 10^{-28}(\overline{\mathrm{BF}}/10^3{)}^{-1}\mathrm{c}{\mathrm{m}}^3{\mathrm{s}}^{-1}$ is needed, where $\overline{\mathrm{BF}}$ is the averaged boost factor of the annihilation signal of these Galaxy Clusters. In this work we discuss several models which could interpret these features and estimate the model parameters. Usually sizeable coupling parameter is needed. The $2\sigma$ upper limits on the cross section of the dark matter annihilation into various final states such as $b\bar{b}$, ${\mu }^{+}{\mu }^{-}$ and so on are also presented.

   hep-phastro-ph.HEPRD(2016)·7 citations
8. 08*

   Refined analysis and updated constraints on general non-standard tbW couplings

   Zenro Hioki (U. Tokushima)🇯🇵 · Kazumasa Ohkuma (Okayama U. Science)🇯🇵 · Akira Uejima (Okayama U. Science)🇯🇵

   We recently studied possible non-standard tbW couplings based on the effective-Lagrangian which consists of four kinds of SU(3) x SU(2) x U(1) invariant dimension-6 effective operators and gave an experimentally allowed region for each non-standard coupling. We here re-perform that analysis much more precisely based on the same experimental data but on a new computational procedure using the Graphics-Processing-Unit (GPU) calculation system. Comparing these two analyses with each other, the previous one is found to have given quite reliable results despite of its limited computation capability. We then apply this new procedure to the latest data and present updated results.

   hep-phhep-exPLB(2016)·5 citations
9. 09*

   Proton Decay Prediction in 5D Gauge-Higgs Unification

   Naoyuki Haba🇯🇵 · Nobuchika Okada🇺🇸 · Toshifumi Yamada🇯🇵

   The Higgs boson mass and top quark mass imply that the Higgs quartic coupling vanishes around the scale of $10^9-10^{13}$ GeV, depending on the precise value of the top quark mass. The vanishing quartic coupling can be naturally addressed if the Higgs field originates from a 5-dimensional gauge field and the 5th dimension is compactified at the scale of the vanishing Higgs quartic coupling, which is a scenario based on gauge-Higgs unification. We present a general prediction of the scenario on the proton decay process $p\to {\pi }^0{e}^{+}$. In many gauge-Higgs unification models, the 1st generation fermions are localized towards an orbifold fixed point in order to realize the realistic Yukawa couplings. Hence, four-fermion operators responsible for the proton decay can appear with a suppression of the 5-dimensional Planck scale (not the 4-dimensional Planck scale). Since the 5-dimensional Planck scale is connected to the compactification scale, we have a correlation between the proton partial decay width and the top quark mass. We show that the future Hyper-Kamiokande experiment may discover the proton decay if the top quark pole mass is larger than about 172.5 GeV.

   hep-phPRD(2016)·1 citation
10. 10*

    Impacts of B-factory measurements on determination of fragmentation functions from electron-positron annihilation data

    M. Hirai🇯🇵 · H. Kawamura🇯🇵 · S. Kumano🇯🇵 · K. Saito🇯🇵

    Fragmentation functions are determined for the pion and kaon by global analyses of charged-hadron production data in electron-positron annihilation. Accurate measurements were reported by the Belle and BaBar collaborations for the fragmentation functions at the center-of-mass energies of 10.52 GeV and 10.54 GeV, respectively, at the KEK and SLAC B factories, whereas other available $e^{+}{e}^{-}$ measurements were mostly done at higher energies, mainly at the $Z$ mass of 91.2 GeV. There is a possibility that gluon fragmentation functions, as well as quark fragmentation functions, are accurately determined by scaling violation. We report our global analysis of the fragmentation functions especially to show impacts of the B-factory measurements on the fragmentation function determination. Our results indicate that the fragmentation functions are determined more accurately not only by the scaling violation but also by high-statistical nature of the Belle and BaBar data. However, there are some tensions between the Belle and BaBar data in comparison with previous measurements. We also explain how the flavor dependence of quark fragmentation functions and the gluon function are separated by using measurements at different $Q^2$ values. In particular, the electric and weak changes are different depending on the quark type, so that a light-quark flavor separation also became possible in principle due to the precise data at both $\sqrt{s}\simeq 10.5$ GeV and 91.2 GeV.

    hep-phhep-exnucl-exnucl-thPTEP(2016)·23 citations
11. 11*

    Dark Matter in Axion Landscape

    Ryuji Daido🇯🇵 · Takeshi Kobayashi🇮🇹 · Fuminobu Takahashi🇯🇵

    If there are a plethora of axions in nature, they may have a complicated potential and create an axion landscape. We study a possibility that one of the axions is so light that it is cosmologically stable, explaining the observed dark matter density. In particular we focus on a case in which two (or more) shift-symmetry breaking terms conspire to make the axion sufficiently light at the potential minimum. In this case the axion has a flat-bottomed potential. In contrast to the case in which a single cosine term dominates the potential, the axion abundance as well as its isocurvature perturbations are significantly suppressed. This allows an axion with a rather large mass to serve as dark matter without fine-tuning of the initial misalignment, and further makes higher-scale inflation to be consistent with the scenario.

    hep-phastro-ph.COPLB(2017)·18 citations
12. 12*

    Precise Determination of the U-235 Reactor Antineutrino Cross Section per Fission

    Carlo Giunti🇮🇹

    We investigate which among the reactor antineutrino fluxes from the decays of the fission products of ${}^{235}\text{U}$, ${}^{238}\text{U}$, ${}^{239}\text{Pu}$, and ${}^{241}\text{Pu}$ may be responsible for the reactor antineutrino anomaly if the anomaly is due to a miscalculation of the antineutrino fluxes. We find that it is very likely that at least the calculation of the ${}^{235}\text{U}$ flux must be revised. From the fit of the data we obtain the precise determination ${\sigma }_{f,235}=(6.33\pm 0.08)\times 10^{-43}{\text{cm}}^2/\text{fission}$ of the ${}^{235}\text{U}$ cross section per fission, which is more precise than the calculated value and differs from it by $2.2\sigma$. The cross sections per fission of the other fluxes have large uncertainties and in practice their values are undetermined by the fit.

    hep-phhep-exnucl-exnucl-thPLB(2017)·41 citations
13. 13*

    Lepton-flavour violation in a Pati-Salam model with gauged flavour symmetry

    Thorsten Feldmann🇩🇪 · Christoph Luhn🇩🇪 · Paul Moch🇩🇪

    Combining Pati-Salam (PS) and flavour symmetries in a renormalisable setup, we devise a scenario which produces realistic masses for the charged leptons. Flavour-symmetry breaking scalar fields in the adjoint representations of the PS gauge group are responsible for generating different flavour structures for up- and down-type quarks as well as for leptons. The model is characterised by new heavy fermions which mix with the Standard Model quarks and leptons. In particular, the partners for the third fermion generation induce sizeable sources of flavour violation. Focusing on the charged-lepton sector, we scrutinise the model with respect to its implications for lepton-flavour violating processes such as $\mu \to e\gamma$, $\mu \to 3e$ and muon conversion in nuclei.

    hep-phJHEP(2016)·15 citations
14. 14*

    An Introduction to the Massive Helicity Formalism with applications to the Electroweak SM

    J. Lorenzo Diaz-Cruz🇲🇽 · Bryan O. Larios🇲🇽 · O. Meza-Aldama🇲🇽

    The power of the helicity formalism has been appreciated recently from its application to the massless case, where plenty of formal aspects of multi-legs amplitudes have been derived. However, in order to extend the formalism to the realistic cases, such as the electroweak Standard Model and QCD with massive quarks, some extra inputs are needed. We discuss first the formalism needed to evaluate amplitudes expressed with the modern notation for massive fermions and vectors based on a thorough treatment of Proca vector fields. Then, we present some examples of elementary processes where it is shown how the formalism leads to tremendous simplifications, these include 2-body decays $Z\to ff$, $h\to ff$ and $h\to W^{-}{W}^{+}$ as well as the 3-body decay $h\to V{f}^{\prime }\bar{f}$.

    hep-phJ.Phys.Conf.Ser.(2016)·15 citations
15. 15*

    Revealing the inner structure of the newly observed $D_2^{\ast }(3000)$

    Jun-Zhang Wang🇨🇳 · Dian-Yong Chen🇨🇳 · Qin-Tao Song🇯🇵 · Xiang Liu🇨🇳 · Takayuki Matsuki🇯🇵

    Stimulated by the recent observation of the $D_2^{\ast }(3000)$, we study the decay behaviors of the $3P$ and $2F$ charmed mesons in the present work. By comparing the masses and decay properties of the $3^3{P}_2$ and $2^3{F}_2$ charmed mesons with the observation of the $D_2^{\ast }(3000)$, we conclude that the most possible assignment of the $D_2^{\ast }(3000)$ is the $3^3{P}_2$ charmed meson, while the assignment of the $2^3{F}_2$ charmed meson could not be fully exclude. The results of the unobserved $3P$ and $2F$ charmed mesons in this work could provide some fundamental information of searching for these charmed mesons in the further experiments by LHCb and forthcoming Belle II.

    hep-phPRD(2016)·17 citations
16. 16*

    Neutrino Mass, Dark Matter and Anomalous Magnetic Moment of Muon in a $U(1{)}_{L_{\mu }-L_{\tau }}$ Model

    Anirban Biswas🇮🇳 · Sandhya Choubey🇮🇳 · Sarif Khan🇮🇳

    The observation of neutrino masses, mixing and the existence of dark matter are amongst the most important signatures of physics beyond the Standard Model (SM). In this paper, we propose to extend the SM by a local $L_{\mu }-L_{\tau }$ gauge symmetry, two additional complex scalars and three right-handed neutrinos. The $L_{\mu }-L_{\tau }$ gauge symmetry is broken spontaneously when one of the scalars acquires a vacuum expectation value. The $L_{\mu }-L_{\tau }$ gauge symmetry is known to be anomaly free and can explain the beyond SM measurement of the anomalous muon $(\mathrm{g}-2)$ through additional contribution arising from the extra $Z_{\mu \tau }$ mediated diagram. Small neutrino masses are explained naturally through the Type-I seesaw mechanism, while the mixing angles are predicted to be in their observed ranges due to the broken $L_{\mu }-L_{\tau }$ symmetry. The second complex scalar is shown to be stable and becomes the dark matter candidate in our model. We show that while the $Z_{\mu \tau }$ portal is ineffective for the parameters needed to explain the anomalous muon $(\mathrm{g}-2)$ data, the correct dark matter relic abundance can easily be obtained from annihilation through the Higgs portal. Annihilation of the scalar dark matter in our model can also explain the Galactic Centre gamma ray excess observed by Fermi-LAT. We show the predictions of our model for future direct detection experiments and neutrino oscillation experiments.

    hep-phJHEP(2016)·105 citations
17. 17*

    Towards NLO calculations in the parton Reggeization approach

    Maxim Nefedov🇷🇺 · Vladimir Saleev🇷🇺

    Parton Reggeization approach is the scheme of kT-factorization for multiscale hard processes, which is based on the Lipatov's gauge invariant effective field theory (EFT) for high energy processes in QCD. The new type of rapidity divergences, associated with the log 1/x-corrections, appears in the loop corrections in this formalism. The covariant procedure of regularization of rapidity divergences, preserving the gauge invariance of effective action is described. As an example application, the one-loop correction to the propagator of Reggeized quark and gamma Q q -scattering vertex are computed. Obtained results are used to construct the Regge limit of one-loop gamma+gamma -> q + barq amplitude. The cancelation of rapidity divergences and consistency of the EFT prediction with the full QCD result is demonstrated. The rapidity renormalization group within the EFT is discussed.

    hep-ph10 citations
18. 18*

    R-ratio of electron-positron annihilation into hadrons: higher-order pi2-terms

    A.V.Nesterenko🇷🇺 · S.A.Popov🇷🇺

    High-energy behavior of R-ratio of electron-positron annihilation into hadrons is studied. In particular, it is argued that at any given order of perturbation theory the re-expansion of the R-ratio in the ultraviolet asymptotic can be reduced to the form of power series in the naive continuation of the strong running coupling into the timelike domain. The convergence range of the re-expanded R-ratio and the corresponding higher-order pi2-terms are discussed.

    hep-phNucl.Part.Phys.Proc.(2017)·4 citations
19. 19*

    Motion of Confined Particles

    David E. Miller🇩🇪 · Dirk Rollmann🇩🇪

    We carry out numerical evaluations of the motion of classical particles in Minkowski Space ${\mathbb{M}}^4$ which are confined to the inside of a bag. In particular, we analyze the structure of the paths evolving from the breaking of the dilatation symmetry, the conformal symmetry and the combination of both together. The confining forces arise directly from the corresponding nonconserved currents. We demonstrate in our evaluations that these particles under certain initial conditions move toward the interior of the bag.

    hep-phhep-thActa Phys.Polon.Supp.(2017)·0 citations
20. 20*

    Sound Attenuation in Quark Matter Due to Pairing Fluctuations

    Boris Kerbikov🇷🇺

    The sound wave in dense quark matter is subject to strong absorption due to diquark field fluctuations above T critical. The result is another facet of Mandelshtam-Leontovich slow relaxation time theory.

    hep-phnucl-thEPJ Web Conf.(2016)·3 citations
21. 21*

    Finite Temperature QCD Sum Rules: a Review

    Alejandro Ayala🇲🇽 · C. A. Dominguez🇿🇦 · M. Loewe🇿🇦

    The method of QCD sum rules at finite temperature is reviewed, with emphasis on recent results. These include predictions for the survival of charmonium and bottonium states, at and beyond the critical temperature for de-confinement, as later confirmed by lattice QCD simulations. Also included are determinations in the light-quark vector and axial-vector channels, allowing to analyse the Weinberg sum rules, and predict the dimuon spectrum in heavy ion collisions in the region of the rho-meson. Also in this sector, the determination of the temperature behaviour of the up-down quark mass, together with the pion decay constant, will be described. Finally, an extension of the QCD sum rule method to incorporate finite baryon chemical potential is reviewed.

    hep-phhep-latnucl-thAdv.High Energy Phys.(2017)·39 citations
22. 22*

    Baryon number fluctuations at finite temperature and density

    Wei-jie Fu🇨🇳 · Jan M. Pawlowski🇩🇪 · Fabian Rennecke🇩🇪 · Bernd-Jochen Schaefer🇩🇪

    We investigate baryon number fluctuations for finite temperature and density in two-flavor QCD. This is done within a QCD-improved low-energy effective theory in an extension of the approach put forward in [1,2]. In the present work we aim at improving the predictive power of this approach for large temperatures and density, that is, for small collision energies. This is achieved by taking into account the full frequency dependence of the quark dispersion. This ensures the necessary Silver Blaze property of finite density QCD for the first time, which so far was only implemented approximately. Moreover, we show that Polyakov loop fluctuations have a sizeable impact at large temperatures and density. The results for the kurtosis of baryon number fluctuations are compared to previous effective theory results, lattice results and recent experimental data from STAR.

    hep-phPRD(2016)·102 citations
23. 23*

    Sound waves in the compactified D0-D4 brane system

    Wenhe Cai🇨🇳 · Si-wen Li🇨🇳

    As an extension to our previous work, we study the transport properties of the Witten-Sakai-Sugimoto model in the black D4-brane background with smeared D0-branes (D0-D4/D8 system). Because of the presence of the D0-branes, in the bubble configuration this model is holographically dual to 4d QCD or Yang-Mills theory with a Chern-Simons term. And the number density of the D0-branes corresponds to the coupling constant ($\theta$ angle) of the Chern-Simons term in the dual field theory. In this paper, we accordingly focus on small number density of the D0-branes to study the sound mode in the black D0-D4 brane system since the coupling of the Chern-Simons term should be quite weak in QCD. Then we derive its 5d effective theory and analytically compute the speed of sound and the sound wave attenuation in the approach of Gauge/Gravity duality. Our result shows the speed of sound and the sound wave attenuation is modified by the presence of the D0-branes. Thus they depend on the $\theta$ angle or chiral potential in this holographic description.

    ↳ hep-thhep-phPRD(2016)·7 citations
24. 24*

    Primordial Gravitational Waves from Axion-Gauge Fields Dynamics

    Emanuela Dimastrogiovanni🇺🇸 · Matteo Fasiello🇺🇸 · Tomohiro Fujita🇺🇸

    Inspired by the chromo-natural inflation model of Adshead&Wyman, we reshape its scalar content to relax the tension with current observational bounds. Besides an inflaton, the setup includes a spectator sector in which an axion and SU(2) gauge fields are coupled via a Chern-Simons-type term. The result is a viable theory endowed with an alternative production mechanism for gravitational waves during inflation. The gravitational wave signal sourced by the spectator fields can be much larger than the contribution from standard vacuum fluctuations, it is distinguishable from the latter on the basis of its chirality and, depending on the theory parameters values, also its tilt. This production process breaks the well-known relation between the tensor-to-scalar ratio and the energy scale of inflation. As a result, even if the Hubble rate is itself too small for the vacuum to generate a tensor amplitude detectable by upcoming experiments, this model still supports observable gravitational waves.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2017)·238 citations
25. 25*

    Hydrodynamic modeling of a pure-glue initial scenario in high-energy hadron and heavy-ion collisions

    V. Vovchenko🇩🇪 · Long-Gang Pang🇩🇪 · H. Niemi🇩🇪 · Iu. A. Karpenko🇺🇦 · M. I. Gorenstein🇺🇦 · L. M. Satarov🇩🇪 · I. N. Mishustin🇩🇪 · B. Kämpfer🇩🇪 · H. Stoecker🇩🇪

    Partonic matter produced in the early stage of ultrarelativistic nucleus-nucleus collisions is assumed to be composed mainly of gluons, and quarks and antiquarks are produced at later times. The comparable hydrodynamic simulations of heavy-ion collisions for (2+1)-flavor and Yang-Mills equations of state performed by using three different hydrodynamic codes are presented. Assuming slow chemical equilibration of quarks, the spectra and elliptic flows of thermal dileptons and photons are calculated for central Pb+Pb collisions at the LHC energy of $\sqrt{s_{{}_{\mathrm{NN}}}}=2.76$ TeV. It is shown that a suppression of quarks at early times leads to a significant reduction of the yield of the thermal dileptons, but only to a rather modest suppression of the $p_T$-distribution of direct photons. It is demonstrated that an enhancement of photon and dilepton elliptic flows might serve as a promising signature of the pure-glue initial state. Calculations based on Bjorken hydrodynamics suggest that collisions of small systems at intermediate energies available at RHIC or future FAIR facilities may show stronger effects associated with initial pure gluodynamic evolution.

    ↳ nucl-thhep-phPoS(2016)·8 citations
26. 26*

    Consequences of simultaneous chiral symmetry breaking and deconfinement for the isospin symmetric phase diagram

    Tobias Fischer🇵🇱 · Thomas Klähn🇵🇱 · Matthias Hempel🇨🇭

    The thermodynamic bag model (tdBag) has been applied widely to model quark matter properties in both heavy-ion and astrophysics communities. Several fundamental physics aspects are missing in tdBag, e.g., dynamical chiral symmetry breaking (D$\chi$SB) and repulsions due to the vector interaction are both included explicitly in the novel vBag quark matter model of Klähn and Fischer (2015) (Astrophys. J. 810, 134 (2015)). An important feature of vBag is the simultaneous D$\chi$SB and deconfinement, where the latter links vBag to a given hadronic model for the construction of the phase transition. In this article we discuss the extension to finite temperatures and the resulting phase diagram for the isospin symmetric medium.

    ↳ nucl-thhep-phEPJA(2016)·6 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.